1. Field of the Invention
This invention relates to welding apparatus and more particularly it concerns improvements to welding apparatus of the type wherein a probe follows deviations of a seam to be welded, a storage device in the form of a settable contour cam is set according to probe movements and a welding torch, which is maintained a fixed distance behind the probe, is driven in accordance with the cam settings so that the torch is positioned in the weld seam.
2. Description of the Prior Art
U.S. Pat. Nos. 3,158,121 and 3,281,047 both describe welding machines wherein a probe tracks a seam to be welded and wherein the tracking movements of the probe are mechanically linked to a pin type contour cam. The contour cam comprises a group of pins mounted side-by-side on a wheel which turns in synchronism with the movements of a probe and following torch assembly with respect to a workpiece being welded. The pins are moved longitudinally on the wheel by the action of the probe as it follows the weld seam deviations on the workpiece; and locking means are provided to hold the pins tightly in place on the wheel after they have been set by the probe. The following torch is mounted to move in the same direction as the probe when it follows the weld seam deviations; and the torch, which is mechanically linked to a follower riding on the pins is thus positioned in accordance with the probe.
In U.S. Pat. No. 3,281,407 two cam wheels are provided, one to record the vertical probe movements and the other to record the lateral probe movements.
In another U.S. Pat. No. 4,068,154, there is described a welding machine in which the probe movements are stated to be converted to digital signals which are processed through shift registers and then are used to drive the torch to corresponding positions.
The welding devices of U.S. Pat. Nos. 3,158,121 and 3,281,047 suffer from disadvantage that the cam pins must be locked by special locking means which are complicated and cumbersome but which are necessary because of the fact that they must move a cam follower which is linked to the torch. Because of this tracking accuracy is unreliable. The welding machine of U.S. Pat. No. 4,068,154 uses digital signal processing which may not be suitable for some applications. Also the storage means in that welding machine is not readily adaptable to variations or adjustments in probe to torch distance.
A further disadvantage of the prior art tracking type welding machines is that they require the use of design cams to follow large contour deviations. These design cams have to be provided with special follower assemblies and they must be replaced for each different workpiece design being welded.